Method and apparatus for eliminating iron oxide dust

ABSTRACT

IRON OXIDE DUST FORMATION AT THE WORK ROLLS IN A HOT ROLLING MILL FOR SHEET STEEL IS ELIMINATED BY ESTABLISHING AN INERT ATMOSPHERE AT THE EXIT SIDE OF THE ROLLS, SPECIALLY CONSTRUCTED UPPER AND LOWER STRIPPERS HAVING NOZZLES MOUNTED THEREIN BEING ARRANGED TO SPRAY AN INERT GAS INTO THE BITE REGION OF THE WORK ROLLS TO ESTABLISH THE INERT ATMOSPHERE.

Oct. 19. 1971 Tygjiap a METHOD AND APPARATUS FOR ELIIIIATIIG IRON OXIDE DUST Filed June 17. 1969 O 2 Sheets-Shoat l nrromvsvs llll.

R A MR 2 Z .T w p i. m m H. 1; a m finanmwimfiw w HFMMFEEPIIF m um'rnon AND APPARATUS FOR mmumm'me mos 0x102 ous'r Filed June 17, 1969 T. A. REPPER Oct. 19, 1971 2 Sheets-"Sheet 2 IN VENTOR Tusoaaes H. PEPPER 63M 4 TTORNE YS United States Patent 3,613,421 METHOD AND APPARATUS FOR ELIMINATING IRON OXIDE DUST Theodore A. Repper, 501 Stanley St., Middletown, Ohio 45042 Filed June 17, 1969, Ser. No. 834,030 Int. Cl. BZlb 9/00, 45/04 US. Cl. 72-38 8 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION (1) Field of the invention The present invention relates generally to the hot rolling of sheet steel from ingots, and more particularly to a method and apparatus for eliminating the formation of iron oxide dust at the work rolls of a hot rolling mill.

(2) Description of the prior art Sheet steel is commonly manufactured by putting a steel ingot through a hot rolling mill, the mill including a plurality of sets of work rolls that progressively work on the steel. There is normally created at the last few roll sets in the series a very fine iron oxide dust, the formation of which is undesirable in that the dust pollutes the atmosphere, and the abrasive qualities thereof can damage motors, bearing surfaces and the like to the point of causing breakdown. I

Because of the undesirable qualities of the oxide dust, collectors are commonly employed in an effort to gather the dust and prevent it from polluting the environment. Vacuum hoods have been fitted over the work rolls to gather the oxide dust, and flowing liquids have been used as a bath to capture the dust. However, even with the best of collectors it is not uncommon for substantial quantities of the undesirable oxide dust to escape.

The most desirable condition would be to eliminate the oxide dust entirely by preventing its formation, and it is toward this goal that the present invention is directed.

SUMMARY OF THE INVENTION In rolling sheet steel starting from an ingot in a hot rolling mill, the ingot is progressively rolled through a series of about 14 sets or stands of work rolls, including the slabbing mill, the roughing mill, and the finishing mill, the latter having anywhere from three to ten pairs of work rolls, the sheet moving faster and getting longer and thinner as it progresses through the rolls. Toward the end of the mill at the finishing mill or stand, in the region of the last few roll sets, an iron oxide dust is normally formed during the rolling process.

It is believed that the iron oxide dust is formed at these last roll sets because of the combination of high pressure exerted on the steel by the work rolls, the speed of the steel sheet, and combustion. All three of these factors have been found to be necessary to produce the oxide dust, and thus the elimination of any one would eliminate its formation. Obviously, roll pressure and the speed of the steel sheet are inherent to the hot rolling process, and thus if dust formation is to be eliminated, combustion must be prevented.

The concept of the present invention is to prevent combustion by establishing an oxygen-free atmosphere on the exit side of the work rolls, which is accomplished by injecting into the bite region an inert gas, say nitrogen, in quantity sufiicient to displace the normally present oxygen. Injection is accomplished by fitting the upper and lower strippers with a plurality of horizontally spaced nozzles directed toward the bite region, which nozzles are connected to a common manifold to which the inert gas is continuously supplied. This novel continuous feed arrangement eliminates the need for any structure enclosing the work rolls, which might otherwise be necessary to maintain the desired inert atmosphere.

It is an object of the present invention to provide a method and apparatus for preventing the formation of iron oxide dust at the work rolls of a hot rolling mill for sheet steel.

Another object is to provide an apparatus for continuously feeding an inert gas into the bite region of the work rolls of a hot rolling mill for steel, to establish an inert atmosphere within said region.

Other objects and many of the attendant advantages of the present invention will become readily apparent from the following description of the preferred embodiment, when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary plan view of a portion of a hot rolling mill, taken substantially on the line 11 of FIG. 2, showing the unique strippers of the inserts, with a portion of the top stripper broken away for clarity, and showing one of the work rolls in phantom lines;

FIG. 2 is a fragmentary transverse sectional view through the top and bottom strippers, taken on the line 2-2 of FIG. 1;

FIG. 3 is an enlarged fragmentary vertical sectional view, taken on the line 3-3 of FIG. 1, through one of the gas nozzles and the manifold of the upper stripper;

FIG. 4 is an enlarged fragmentary vertical sectional view similar to FIG. 3, through one of the gas nozzles and the manifold of the lower stripper; and

FIG. 5 is an enlarged axial sectional view of one of the gas port nozzles.

DESCRIPTION OF THE PREFERRED EM B ODIMENTS Referring now to the drawings, the inlet end of a conventional finishing stand 2 in a hot rolling mill is shown in FIGS. 1 and 2. Mounted in front of the finishing stand 2 are the upper and lower work rolls 4 and 6, respectively, of a roll set 8. The sheet of steel being rolled passes between the work rolls 4 and 6 and into the finishing stand 2, the sheet moving very rapidly and being under great pressure at the roll set 8.

Mounted at the inlet of the finishing stand 2 are upper and lower stripper assemblies 10 and 12, which function in the conventional manner to keep the fast moving steel sheet from curling and following either one of the work rolls 4 and 6. The upper stripper assembly 10 includes axially disposed bracket arms 14 having a plate 16 welded to the bottom edges thereof, the plate 16 including a flat forward portion 18 and a rounded heel portion 20. The bracket arms 14 carry upper and lower cross shafts 22 and 24, respectively, which are received within slots 26 formed in the structure of the finishing stand 2 for supporting the upper stripper assembly 10. The forward ends of the bracket arms 14 butt against and are welded to a flange 28 formed on the forward edge of the plate 16, and transverse brace bars 30 are welded between the arms 14 and to the top surface of the plate 14 to give stability to the structure.

Secured to the flange 28 is a stripper nose assembly 32, comprising a scraper bar 34 having an upright flange 36 welded to the rear edge thereof, the assembly 32 being fastened to the flange 28 by bolts 38 passing through the flange 36. The forward upper surface 40 of the scraper bar 34 is tapered to define a sharp leading edge 42 on said bar, the surface 40 having an angle such that it normally is generally tangent to the upper work roll 4.

The scraper bar 34 has a plurality of axially extending, horizontally closely spaced, angled stepped bores 44 therein, each bore 44 including an enlarged inlet portion 46, an intermediate portion 48, and a reduced outlet portion 50, the portions 48 and 50 being connected by a tapered wall 51. Typically, the intermediate bore portion 48 is about 2" long and has a diameter of about and the reduced bore portion 50 .will have a diameter of about 75 the stepped bores 44 being horizontally spaced about 1" apart. The stepped bores 44 have an angle to the horizontal chosen so that the axis thereof is directed onto the top surface of a steel sheet being rolled just forward of the bite of the work rolls 4 and 6.

A nozzle 52 is received in each outlet bore portion 50, and comprises a cylindrical body about /2" in length and having an axial bore 54 therethrough with a diameter of about 0.041. The inlet end of the nozzle 52 has a 90 chamfer 56 therein, and said nozzle 52 functions to accurately direct a stream of inert gas toward the bite region of the roll set 8.

An inverted angle iron 58 is welded along its front and rear edges to the top surface of the scraper plate 34 over the 'bore inlets 46 to define a manifold chamber 60 communicating with all of the bores 44, the opposite ends of the chamber 60 being closed by end plates 62 welded to the angle iron 58 and the plate 34. A plurality of spaced brace bars 64 (FIG. 1) are welded between the angle iron 58 and the flange 36, and centrally of said angle iron 58 a pair of closely spaced plates 66 is welded between said angle iron and said flange 36 and to the plate 34, to form the sidewalls of a supply chamber 68. A top plate 69 is welded to the side plates 66, the angle iron 58, and the flange 36 to close the chamber 68, and the angle iron 58 and the flange 36 have supply ports 70 and 72 therein, respectively.

The flange 28 has a larger diameter bore 74 therein positioned to confront the bore 72, and one end of a fitting 76 is secured within said bore. The other end of the fitting 76 is connected to one end of a supply conduit 78, which leads to a source of inert gas (not shown).

The lower stripper assembly 12 includes a front portion 80 and a rear portion 82, the latter comprising a plate 84 having an L-shaped anchor flange 86 on the lower surface thereof that is received in a recess 88 formed in the structure of the finishing stand 2. The front portion 80 of the stripper assembly 12 includes a scraper plate 90 having an L-shaped anchor flange 92 welded to the undersurface thereof along its rear edge, the flange 92 being received in a recess 94 in the finishing stand 2.

The lower stripper plate 90 projects forwardly toward the roll set 8 a further distance than the upper stripper plate 34, and the lower front surface 96 thereof is tapered to provide a sharp leading edge 98, the tapered surface 96 lying generally tangent to the lower roll 6. The lower stripper plate 90 has a plurality of stepped, horizontally spaced bores 100 therein that correspond to the stepped bores 44, and which are also fitted at their outlet ends with nozzles 52. An inverted angle iron 102 is welded to the undersurface of the stripper plate 90 over the bores 100 to define a manifold chamber 104, the opposite ends of the chamber 104 being closed by end plates 106. Medially thereof the rear flange of the angle iron 102 has a hole 108 therein in which one end of a fitting 110 is welded, the other end of the fitting 110 being connected to one end of a supply conduit 112.

The stepped bores 100 and the nozzles 52 fitted therein are positioned to direct a stream of inert gas onto the lower surface of a steel sheet being rolled, just forward of the bite region of the roll pair 8. Thus, the combined sprays from the'upper and lower nozzles 52 are effective to totally bathe the roll set bite region in an inert gas.

While the use of other inert gases is possible, nitrogen has been found to be most desirable, particularly since it often is easily available in a hot rolling mill. By continuously supplying nitrogen to the manifold chambers 60 and 104, so that the one inch-apart upper and lower nozzles 52 have an ample continuous supply, it is possible to bathe the hot and fast moving steel sheet in inert gas in the bite region of the work roll set 8 so that all oxygen is displaced. It has been found that by thus eliminating oxygen and instead establishing an inert atmosphere in the bite region, there will be no formation of the normally found iron oxide dust.

Because the nozzles 52 are continuously supplied with inert gas, and because they are constructed and arranged to direct a stream into the small, critical bite region of the work rolls 4 and 6, there is no need to shroud or otherwise attempt to enclose said work rolls. Rather, it is an easy matter to maintain the inert atmosphere without such shrouds. It is to be understood that upper and lower stripper assemblies 10 and 12 are to be provided at each set of work rolls where the formation of iron oxide dust would otherwise be expected to occur. a

It is readily seen that one advantage of the present invention is that no extensive modifications to an existing hot rolling mill are required. Rather, it is only necessary to install the stripper assemblies of the invention at the specific work roll locations where oxide dust formulation can otherwise occur.

Obviously, many modifications and variations of the invention are possible.

I claim:

1. In a hot rolling mill for steel, said mill including at least one set of work rolls, the method for preventing the formation of iron oxide dust at said set of work rolls during the passage therethrough of a sheet of steel being rolled, comprising continuously directing an inert gas solely into the bite region on the exit side of said set of work rolls both above and below said sheet of steel, to establish an inert atmosphere in said bite region.

2. In a hot rolling mill for steel, the method as recited in claim 1, wherein said inert atmosphere is established by continuously spraying an inert gas into said bite region above and below said sheet of steel, in quantity sufiicient to displace all oxygen from said bite region.

3. In a hot rolling mill for steel, the method as recited in claim 2, wherein said inert gas is sprayed into said bite region from a plurality of closely spaced positions extending transversely across the width of said sheet of steel, said positions being arranged in an upper set disposed above said sheet of steel, and a lower set disposed below said sheet of steel.

4. In a hot rolling mill for steel, the method as recited in claim 2, wherein said inert gas is nitrogen.

5. In a hot rolling mill for steel, said mill including at least one set of work rolls through which a sheet of steel being hot rolled is passed, means mounted on the exit side of said set of work rolls arranged to continuously spray an inert gas solely into the bite region of said work rolls both above and below said sheet of steel, to establish an inert atmosphere in said bite region for preventing the formation of iron oxide dust at said set of work rolls.

6. In a hot rolling mill for steel, said mill including at least one set of work rolls through which a sheet of steel being hot rolled is passed; a finishing stand on the exit side of said roll set; and upper and lower stripper assemblies carried by said finishing stand and extending into the bite region of said work rolls, each of said stripper assemblies having nozzle means directed solely into said bite region; and means connected with said nozzle means for continuously supplying an inert gas thereto, whereby said 5 gas is sprayed into said bite region in quantity suflicient to displace all oxygen from said bite region for preventing the formation of iron oxide dust at said set of work rolls.

7. In a hot rolling mill for steel as recited in claim 6, wherein said upper and lower stripper assemblies each includes a stripper plate disposed to extend transversely across said sheet of steel; and wherein said nozzle means comprises a first plurality of nozzles mounted within bores in the upper one of said stripper plates, said nozzles being directed downwardly and into the upper bite region of said rolls and being spaced closely across the width of said sheet of steel; and a second plurality of nozzles mounted within bores in the lower one of said stripper plates, said nozzles being directed upwardly and into the lower bite region of said rolls and being spaced closely across the width of said sheet of steel.

8. In a hot rolling mill for steel as recited in claim 7, wherein said means connected with said nozzle means for supplying an inert gas thereto comprises: means forming a first manifold chamber on the upper surface of the upper one of said stripper plates, said first manifold chamber being in communication with all of said first plurality of nozzles; means forming a second manifold chamber on the lower surface of the lower one of said stripper plates,

said second manifold chamber being in communication with all of said second plurality of nozzles; and conduit means connected with both said first and said second manifold chambers, for conducting an inert gas thereto.

References Cited UNITED STATES PATENTS 1,916,677 7/1933 Lloyd 72-236 1,994,691 3/1935 Dahl et al 72236 2,088,241 7/1937 Irvin 72--202 2,230,897 2/1941 McBain et al. 72-201 2,234,153 3/1941 Herbert 7239 2,648,241 8/1953 Bores 72-39 2,711,660 6/1955 Friedman 72-38 3,257,835 6/1966 Cofer et al. 7238 1,968,442 7/1934 Clark et al. 72-38 RICHARD J. HERBST, Primary Examiner E. M. COMBS, Assistant Examiner US. Cl. X.R. 72-39, 236, 365 

